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This paper summarizes the ab-initio electronic and phonon band structures and the temperature-dependent carrier transport in layered Ti2AlC. It is found that the cylindrical Fermi surface is the origin of the anisotropic carrier effective mass (infinite effective mass along the c axis), which leads to a strong anisotropic (insulator along the c axis and metallic along the layer) carrier transport in these films. Using electronic and phonon band structure calculations, we have developed an analytical model for the carrier-phonon interaction and the in-plane carrier conductivity originating from the strong inter-valley (s → d) scattering in Ti2AlC. The density functional theory is used to calculate the average deformation potential corresponding to the acoustic phonon vibrations. The calculated deformation potential is in good agreement with the extracted deformation potential from the transport data available in the literature. The extracted deformation potential will be useful for predicting the transport quantities of these metals at elevated temperatures. [ABSTRACT FROM AUTHOR]

Hierarchically macro-porous lumino-magnetic yttrium aluminium oxide (YAlO:- YAT: tetragonal; YAG: garnet; YAM: monoclinic) ceramic nanophosphors doped with trivalent cerium (Ce) ions have been synthesized by a novel and versatile self assembly route without the need of any external templates. X-ray diffraction and X-ray photoelectron spectroscopy studies confirm the presence of dopant and its valence state. Room temperature ferromagnetism in undoped and YAlO:Ce suggest an intrinsic nature of ferromagnetism dependent on host lattice imperfection along with yellow photoluminescence emission explicitly arising due to Ce doping established the non-interfering character of the two phenomena. Such a porous morphology has the potential of the biocarriers and could be engineered to make it suitable for spintronic applications by incorporation of dielectric into the pores and in conjunction with blue light emitting devices which could be used to obtain white light. [ABSTRACT FROM AUTHOR]

A study using a model based on proton motion within a metastable defect complex proved that the light-induced degradation of amorphous silicon solar cells can be shifted through the use of a strong electric field in the dark. This reverse effect is later found to be accelerated by the exposure of the solar cell to intense illumination. This study has demonstrated that reversal rate is influenced by field strength, temperature and light intensity.

The anisotropic optical, electrical and structural properties of indium gallium arsenide/gallium arsenide (InxGa1-xAs/GaAs) single heterostructures were examined via photoluminescence, ellipsometry, micro-Raman and Hall measurements. The InxGa1-xAs layer was grown on a slightly misoriented GaAs substrate via low-pressure metalorganic vapor phase epitaxy. The influence of substrate orientation on the growth process and properties of the heterostructures were also investigated. Secondary and transmission electron microscopic studies were also done on these heterotructures. Results of these investigations are presented for indium compositions between 0.03 and 0.20.

Scattering of coherent light from scattering particles causes phase shift to the scattered light. The interference of unscattered and scattered light causes the formation of speckles. When the scattering particles, under the influence of an ultrasound (US) pressure wave, vibrate, the phase shift fluctuates, thereby causing fluctuation in speckle intensity. We use the laser speckle contrast analysis (LSCA) to reconstruct a map of the elastic property (Young's modulus) of soft tissue-mimicking phantom. The displacement of the scatters is inversely related to the Young's modulus of the medium. The elastic properties of soft biological tissues vary, many fold with malignancy. The experimental results show that laser speckle contrast (LSC) is very sensitive to the pathological changes in a soft tissue medium. The experiments are carried out on a phantom with two cylindrical inclusions of sizes 6mm in diameter, separated by 8mm between them. Three samples are made. One inclusion has Young's modulus E of 40kPa. The second inclusion has either a Young's modulus E of 20kPa, or scattering coefficient of μs'=3.00mm-1 or absorption coefficient of μa=0.03mm-1. The optical absorption (μa), reduced scattering (μs') coefficient, and the Young's modulus of the background are μa=0.01mm-1, μs'=1.00mm-1 and 12kPa, respectively. The experiments are carried out on all three phantoms. On a phantom with two inclusions of Young's modulus of 20 and 40kPa, the measured relative speckle image contrasts are 36.55% and 63.72%, respectively. Experiments are repeated on phantoms with inclusions of μa=0.03mm-1, E=40kPa and μs'=3.00mm-1. The results show that it is possible to detect inclusions with contrasts in optical absorption, optical scattering, and Young's modulus. Studies of the variation of laser speckle contrast with ultrasound driving force for various values of μa, μs', and Young's modulus of the tissue mimicking medium are also carried out. [ABSTRACT FROM AUTHOR]

Phase transformations of annealed bulk 0.955Pb(Zn1/3Nb2/3)O3–0.045PbTiO3 (PZN-4.5%PT) single crystals have been examined by means of dielectric permittivity, thermal current, domain structure, and high-resolution synchrotron x-ray diffraction as a function of temperature. The result shows that annealed (unpoled) bulk PZN-4.5%PT single crystal undergoes an R-T-C transformation sequence upon zero-field heating, where R, T, and C are the rhombohedral, tetragonal, and cubic phases, respectively. Diffractions pertaining to rhombohedral and tetragonal nanotwins are detected. These diffractions can easily be mistaken as the monoclinic diffractions, which, however, are not supported by our thermal current measurement. The nanotwin structure plays an important role in bridging the R-T and T-C transformations, possibly by alleviating the accompanying transformation stresses. [ABSTRACT FROM AUTHOR]

The origin of the extremely broad peak at the lower 2θ side of the main (002) rhombohedral x-ray peak in an unpoled (001)-cut Pb(Zn1/3Nb2/3)0.955Ti0.045O3 (PZN-4.5%PT) single crystal has been examined. This peak, located at about 2θ∼43°–44°, was absent on fractured surfaces of the crystal but reappeared when the fractured surfaces were polished mechanically. High-resolution synchrotron x-ray mesh scans revealed that the as-polished surface was covered with a “deformed layer” of heavily stressed rhombohedral phase of monoclinic symmetry having its c axis lying perpendicular to the surface. This deformed phase can be structurally likened to one full of “incipient monoclinic nuclei/phases,” which are microscopic in size and subject to intense compression in the plane of the surface. With a given polishing direction, this surface layer showed parallel domain patterns when viewed under the polarized light microscope. This surface layer could be largely eliminated by appropriate poling at 0.7–1.5 kV/mm at room temperature but became resistant to poling after annealing. [ABSTRACT FROM AUTHOR]

The modulated single light source and multiple detectors are utilized to study the development and performance of diffuse optical tomography (DOT) system. The results showed that experimental single source system with additional inputs such as 2D input/output modulation depth and air fiber interface correction are capable of detecting 5 and 6 mm inhomogeneities separately and also identify the size difference of multiple inhomogeneities such as 6 and 8 mm.

Deals with a study which characterized the dislocation structure in InGaAs/GaAs strained-layer superlattices by transmission electron microscopy. Characteristics of dislocations; Barrier to dislocation propagation; Existence of extended dislocations which are potentially electrically active defects; Burgers vector characterization of V-shaped dislocations.

Reports on the characterization of epitaxial films of cobalt silicide grown on (001) silicon (Si) molecular beam epitaxy by transmission electron microscopy. Preparation of the epitaxial layers; Information on the crystallographic stability.

Presents a study that evaluated the stability of multijunction amorphous hydrogenated silicon-based solar cells. Effect of current balance on the stability of the solar cells; Analysis of the degradation of single-junction cells; Influence of illumination intensity on the normalized efficiency of the solar cells.

Presents the measurement results of the annealing of photodegraded amorphous silicon p-i-n solar cells. Kinetics of the annealing behavior of amorphous silicon solar cells; Characterization of the annealing process; Comparison of the annealing curves of cells with and without dopants in the i layer.

The amorphous-to-crystalline transformation of Al2O3 thin films grown on a silicon substrate after exposure to electron beams was investigated using in situ transmission electron microscopy. The results showed that there was a critical electron beam dose rate for the transformation. This indicated that electron beam thermal activation was needed for the transition. Nucleation was more homogenous and much more rapid when the electron beam dose rte was higher.